Patients groups have expressed concern the latest screening scandal could further undermine public faith in the system.

Samia al Qadhi, Chief Executive of Breast Cancer Care, said “Even hearing there’s the possibility of further issues with invitations to breast screening will compound the anxiety and uncertainty felt by many women after the awful failings earlier this year. If there have been problems they must be tackled urgently.”

The charity urged women to attend regular screenings , saying it was the way of spotting early stage cancer.

“While there are two sides to the coin for screening it remains our best tool for detecting breast cancer at the earliest possible stage,” said Ms al Qadhi.

Sara Hiom, Cancer Research UK’s director of early diagnosis, said: “If people have missed bowel or breast screening invitations as a result of these errors then that is extremely concerning - our cancer screening programmes are of a very high standard and detect cancers at the earliest stages when they are much more likely to be effectively treated.

The investigation is understood to be at an early stage and there is currently no direct evidence any patients have been harmed.

But a document by officials from NHS England and NHS Improvement document, obtained by the Health Service Journals (HSJ), show concerns about potential “risk of harm” to patients associated with 120,000 discrepancies between two national IT NHS systems.

Ms Hiom added: “It's concerning to hear of further problems with NHS technology, especially if people have inadvertently missed screening, vaccinations or care as a result.

"Our health and social care system deserves to be supported by consistently reliable, 21st century IT, as well as seamless integration between all patient registers and electronic databases - this needs adequate attention and investment.”